Magnetic core



struction of such cores,

Patented 25, 1927.

UNITED STATES PATENT oFFrcE.

WALTHER EHLEBS, 0F BEBLIN-GBUNAU, GERMANY, ASSIGNOR TO GENERAL ELEC- TRIC COMPANY, A CORPORATION OFNEW YORK.

MAGNETIC 001m.

lie-Drawing. Application filed March 14, 1925, Serial No. 15.697. and in Germany April 10,1924.

My present invention relates to the construction of-magnetic cores such, for example, as those adapted for use in connection with telephone circuits. I

Magnetic cores formed of compressed mixtures of insulating material and magnetic material 'have been used to a considerable extent in telephone practice. In the conhowever, it is practically impossible toproduce a uniform compression throughout the entire mass. practice the edges or outer portions become more compressed than the interior portions and as a "result the insulation between the magnetic particles at the outer portions. is c'onsiderably less than the insulation between the magnetic particles in the interior portions, and the edges or outer portions furnish an unproportionally large percentage of the energy losses because of eddy currents be-' tween individual particles.

To overcome this difiiculty it has been proposed to form a core by assembling a sufficient number of fiat pressed pieces to form the desired body. Such construction, however, greatly increases the cost of manufacture.

The object of my invention is to provide a form of magnetic core in which the disadvantages pointed out may be overcome, and in which the insulation between the magnetic particles at the points subjected to the greatest pressure will be as great as at other points in the core.

The object of my invention may be at-v tained in various ways. One way otaccomplisliing'the desired result is to fill difierent parts" of the pres tures,,that is, th mixture in the outer or edge portion of the form may have a greater proportion of insulating material than the mixture in the central, or inner, portion. ()n the other hand, different insulating materials may be used for the different mixtures, the mixture used for the outer porpressed miriture of pressed magnetic form with different mixtions having an insulating material of supcrior insulating properties to that used in the central portions. I

in carrying my invention into eli'ect a wide variety of finely divided insulating materials may be employed, such, for example, as resinous material, glass or various ceramic materials.

Similar results may be obtained by impregnating the pressed body from the outside. By this means the insulation of the outer more highly compressed portions of the core may be increased so'as to be substantially as strong as that of the inner portions. The proportion of insulating material" preseut-in the outer portion of the core may by this method be increased above that present in the inner portion.

\Vhat I claim as new and desire to secure by Letters Patent of the United States, is

1. A magnetic core formed of a comof magnetic material and insulating material, and havingin the densest portions thereof a relatively greater proportion of insulating material than the proportions which areless dense.

2. A magnetic core comprising a compressed mixture ot magnetic material and insulating material and having in its outer portionsa relatively greater proportion of insulating material than in its inner portion. 1 Y

,3. In the construction of a magneticcore material and insulating material the method of compensating for differences in insulation strength due to differences in pressure which consists" in providing in the parts subjectedtb the greatest ressure a relatively greater proportion of insulating material than in the parts subjeeted to lower pressures.

. In Witness whereof, I have hereunto set my hand this 17th day of February, 1925.

WALTHER EHLERS. 

